edited by Mark D'Esposito Neurological Foundations of Cognitive Neuroscience
Contents Preface ix 1 Neglect:A Disorder of Spatial Attention 1 Anjan Chatterjee Balint's Syndrome:A Disorder of Visual Cognition Robert Rafal 3 Amnesia:A Disorder of Episodic Michael S.Mega 4 Semantic Dementia:A Disorder of Semantic Memory 67 John R.Hodges Topographical Disorientation: A Disorder of Way-Finding Ability 89 Geoffrey K.Aguirre 6 Acquired Dyslexia:A Disorder of Reading 109 H.Branch Coslett 7 Acalculia:A Disorder of Numerical Cognition 129 Darren R.Gitelmar guage Production 165 Michael P.Alexander 9 Wernicke Aphasia:A Disorder of Central L anguage Processing 175 Jeffrey R.Binder Apraxia:A Disorder of Motor Control 239 Scott Grafton 11 Lateral Prefrontal Syndrome: A Disorder of Executive Control 259 Robert T.Knight and Mark D'Esposito Contributors 281 Index 283
Preface ix 1 Neglect: A Disorder of Spatial Attention 1 Anjan Chatterjee 2 Bálint’s Syndrome: A Disorder of Visual Cognition 27 Robert Rafal 3 Amnesia: A Disorder of Episodic Memory 41 Michael S. Mega 4 Semantic Dementia: A Disorder of Semantic Memory 67 John R. Hodges 5 Topographical Disorientation: A Disorder of Way-Finding Ability 89 Geoffrey K. Aguirre 6 Acquired Dyslexia: A Disorder of Reading 109 H. Branch Coslett 7 Acalculia: A Disorder of Numerical Cognition 129 Darren R. Gitelman 8 Transcortical Motor Aphasia: A Disorder of Language Production 165 Michael P. Alexander 9 Wernicke Aphasia: A Disorder of Central Language Processing 175 Jeffrey R. Binder 10 Apraxia: A Disorder of Motor Control 239 Scott Grafton 11 Lateral Prefrontal Syndrome: A Disorder of Executive Control 259 Robert T. Knight and Mark D’Esposito Contributors 281 Index 283 Contents
Preface It is an exciting time for the discipline of cogni- and functional neuroimaging studies of both normal tive neuroscience.In the past 10 years we have individuals and neurological patients-aimed at witnessed an explosion in the development and understanding the neural mechanisms underlying advancement of methods that allow us to precisely the cognitive functions affected in each particular examine the neural mechanisms underlving cog clinical syndrome.In many chapters,there are con- nitive processes.functional magnetic resonance flicting data derived from different methodologies ing.for example,has provided markedly im- and the authors have tried to reconcile these differ- proved spatial and temporal resolution of brain ences.Often these attempts at understandine how structure and function.which has led to answers to these data may be converg ent,rather than diverg new questions,and the reexamination of old ques has shed new light on the cognitive mechanisms tions Howe ver.in my inion.the explosive im that functional neur oimaging has had on goal of preparing this book was not to simply may in s clin obehavioral 6 with brain da rom our the study of Such descriptions can be found in excellent window into the al and Thus. Nor was the oal to creating neuro The ouldhiehiehy ook is to con the st nts of the clin nical udy of on in s my hope that reac chapter the varie vill of cognitive neu Anjan Ch aptly at understan chapter on neglect synd ne: ction can be cause for al m if the udying the abnormal bra n.The neglect research was to es abl a unifi from patients with neurological and psy mprenen ve theory of clinic syndrom chiatric disorders provided the foundation for the However.when neglect is used to understand the discipline of cognitive neuroscience and should organization of spatial attention and representatior continue to be an important methodological tool then the behavioral heterogeneity is actually critical in future studies. to its use as an investigative tool.These words Each chapter in this book was written by a neu capture perfectly my intent for this book rologist who also practices cognitive neuroscience. Many neurologists in training and in practice Each chapter begins with a description of a case lack exposure to cognitive neuroscience.Similarly. report.often a patient seen by the author.and many newly trained cognitive neuroscientists describes the symptoms seen in this patient,laying lack exposure to the rich history of investigations the foundation for the cognitive processes to be of brain-behavior relationships in neurological explored.After the clinical description.the authors patients.I am optimistic that this book will serve have provided a historical background about what both groups well.It is a privilege to have assembled we have learned about these particular neurobe an outstanding group of neurologists and cognitive havioral syndromes through clinical observation neuroscientists to present their unique perspective and neuropsychological investigation.Each chapter on the physical basis of the human mind. then explores investigations using a variety of methods-single-unit electrophysiological record- ing in awake-behaving monkeys,behavioral studies of normal healthy subjects.event-related potential
It is an exciting time for the discipline of cognitive neuroscience. In the past 10 years we have witnessed an explosion in the development and advancement of methods that allow us to precisely examine the neural mechanisms underlying cognitive processes. Functional magnetic resonance imaging, for example, has provided markedly improved spatial and temporal resolution of brain structure and function, which has led to answers to new questions, and the reexamination of old questions. However, in my opinion, the explosive impact that functional neuroimaging has had on cognitive neuroscience may in some ways be responsible for moving us away from our roots—the study of patients with brain damage as a window into the functioning of the normal brain. Thus, my motivation for creating this book was to provide a collection of chapters that would highlight the interface between the study of patients with cognitive deficits and the study of cognition in normal individuals. It is my hope that reading these chapters will remind us as students of cognitive neuroscience that research aimed at understanding the function of the normal brain can be guided by studying the abnormal brain. The incredible insight derived from patients with neurological and psychiatric disorders provided the foundation for the discipline of cognitive neuroscience and should continue to be an important methodological tool in future studies. Each chapter in this book was written by a neurologist who also practices cognitive neuroscience. Each chapter begins with a description of a case report, often a patient seen by the author, and describes the symptoms seen in this patient, laying the foundation for the cognitive processes to be explored. After the clinical description, the authors have provided a historical background about what we have learned about these particular neurobehavioral syndromes through clinical observation and neuropsychological investigation. Each chapter then explores investigations using a variety of methods—single-unit electrophysiological recording in awake-behaving monkeys, behavioral studies of normal healthy subjects, event-related potential and functional neuroimaging studies of both normal individuals and neurological patients—aimed at understanding the neural mechanisms underlying the cognitive functions affected in each particular clinical syndrome. In many chapters, there are con- flicting data derived from different methodologies, and the authors have tried to reconcile these differences. Often these attempts at understanding how these data may be convergent, rather than divergent, has shed new light on the cognitive mechanisms being explored. The goal of preparing this book was not to simply describe clinical neurobehavioral syndromes. Such descriptions can be found in many excellent textbooks of behavioral and cognitive neurology. Nor was the goal to provide a primer in cognitive neuroscience. The goal of this book is to consider normal cognitive processes in the context of patients with cognitive deficits. Each of the clinical syndromes in this book is markedly heterogeneous and the range of symptoms varies widely across patients. As Anjan Chatterjee aptly states in his chapter on the neglect syndrome: “This heterogeneity would be cause for alarm if the goal of neglect research was to establish a unified and comprehensive theory of the clinical syndrome. However, when neglect is used to understand the organization of spatial attention and representation, then the behavioral heterogeneity is actually critical to its use as an investigative tool.” These words capture perfectly my intent for this book. Many neurologists in training and in practice lack exposure to cognitive neuroscience. Similarly, many newly trained cognitive neuroscientists lack exposure to the rich history of investigations of brain–behavior relationships in neurological patients. I am optimistic that this book will serve both groups well. It is a privilege to have assembled an outstanding group of neurologists and cognitive neuroscientists to present their unique perspective on the physical basis of the human mind. Preface
Neglect:A Disorder of Spatial Attention Anjan Chatterjee produce subtle differences in deficits of these ptentmay meglect pants oftheiro bod are of A fferences themselve: tion and represen tions through the syndrome of parts of their environment,and even parts of scenes neglect is possible precisely because neglect is in their imagination.This clinical syndrome is pro- heterogeneous (Chatterjee,1998). duced by a lateralized disruption of spatial attention and representation and raises several questions of interest to cognitive neuroscientsts.How do humans Case Report represent space?How do humans direct spatial attention?How is attention related to perception? Neglect is How is attention related to action? with left brain d Spatial attention and representation can also be neglect following right brain damage.although similar studied in humans with functional neuroimaging deficits are seen sometimes following left brain damage. and with animal lesion and single-cell neurophysi- A 65-year-old woman presented to the hospital becaus She w ethargic Ior ological studies.Despite the unique methods and weakne approaches of these different disciplines,there is considerable convergence in our understanding of ber left hand was held in front of ber eves.she sug how the brain organizes and represents space.In that the limb belonged to the examiner.As her level of this chapter.I begin by describing the clinical syn- arousal improved.she continued to orient to her right.even drome of neglect.Following this description.I when approached and spoke outline the major theoretical approaches and bio- the foo ie of h logical correlates of the clinical phenomena.I then turn to prominent issues in recent neglect research Her speech was mildly dysarthric.She answered and to relevant data from human functional neuro questions correctly.but in a flat tone.Although her imaging and animal studies.Finally,I conclude with conversation was superficially appropriate.she seemed several issues that in my view warrant further unconcered about her condition or even about being in the hosp en why sh consideration As a prelude.it should be clear that neglect is When rofe to he .she neous disorder.Its manifestations vary would look at and lift her right arm.Over several days considerably across patients (Chatteriee.1998 after hearing from her physicians that she had had a stroke Halligan Marshall.1992.1998).This hete m if the s oal of PIst【o move er ler ged h arch v to establish nsive the clinical noted that she was pleasant and enga ng for short periods r when d de d the but not particularly motivated during therapy sessionsand e fatigued easily. oral heterogeneity y is actually critica nths after her ns use as eft-sike e.obvious signs attention, on,and sensation on the left.but after about 6 months she also damage to parts of these networks can experienced uncomfortable sensations both on the skin and"inside"her left arm.The patient continued to fatigue
Anjan Chatterjee Unilateral spatial neglect is a fascinating clinical syndrome in which patients are unaware of entire sectors of space on the side opposite to their lesion. These patients may neglect parts of their own body, parts of their environment, and even parts of scenes in their imagination. This clinical syndrome is produced by a lateralized disruption of spatial attention and representation and raises several questions of interest to cognitive neuroscientsts. How do humans represent space? How do humans direct spatial attention? How is attention related to perception? How is attention related to action? Spatial attention and representation can also be studied in humans with functional neuroimaging and with animal lesion and single-cell neurophysiological studies. Despite the unique methods and approaches of these different disciplines, there is considerable convergence in our understanding of how the brain organizes and represents space. In this chapter, I begin by describing the clinical syndrome of neglect. Following this description, I outline the major theoretical approaches and biological correlates of the clinical phenomena. I then turn to prominent issues in recent neglect research and to relevant data from human functional neuroimaging and animal studies. Finally, I conclude with several issues that in my view warrant further consideration. As a prelude, it should be clear that neglect is a heterogeneous disorder. Its manifestations vary considerably across patients (Chatterjee, 1998; Halligan & Marshall, 1992, 1998). This heterogeneity would be cause for alarm if the goal of neglect research were to establish a unified and comprehensive theory of the clinical syndrome. However, when neglect is used to understand the organization of spatial attention and representation, then the behavioral heterogeneity is actually critical to its use as an investigative tool. Distributed neuronal networks clearly mediate spatial attention, representation, and movement. Focal damage to parts of these networks can 1 Neglect: A Disorder of Spatial Attention produce subtle differences in deficits of these complex functions. These differences themselves are of interest. A careful study of spatial attention and representations through the syndrome of neglect is possible precisely because neglect is heterogeneous (Chatterjee, 1998). Case Report Neglect is more common and more severe with right than with left brain damage. I will refer mostly to left-sided neglect following right brain damage, although similar deficits are seen sometimes following left brain damage. A 65-year-old woman presented to the hospital because of left-sided weakness. She was lethargic for 2 days after admission. She tended to lie in bed at an angle, oriented to her right, and ignored the left side of her body. When her left hand was held in front of her eyes, she suggested that the limb belonged to the examiner. As her level of arousal improved, she continued to orient to her right, even when approached and spoken to from her left. She ate only the food on the right side of her hospital tray. Food sometimes collected in the left side of her mouth. Her speech was mildly dysarthric. She answered questions correctly, but in a flat tone. Although her conversation was superficially appropriate, she seemed unconcerned about her condition or even about being in the hospital. When asked why she was hospitalized, she reported feeling weak generally, but denied any specific problems. When referring to her general weakness, she would look at and lift her right arm. Over several days, after hearing from her physicians that she had had a stroke and having repeatedly been asked by her physical therapist to move her left side, she acknowledged her left-sided weakness. However, her insight into the practical restrictions imposed by her weakness was limited. Her therapists noted that she was pleasant and engaging for short periods, but not particularly motivated during therapy sessions and fatigued easily. Three months after her initial stroke, obvious signs of left neglect abated. Her left-sided weakness also improved. She had slightly diminished somatosensory sensation on the left, but after about 6 months she also experienced uncomfortable sensations both on the skin and “inside” her left arm. The patient continued to fatigue
Anjan Chatterjee 2 eshowing esion in the posterior division of the right middle erera artery involving the inferior parietal lobule and the posterior superior temporal gyrus. easily and remained at hon much of the time.Her mg ership lim artery (figure 1.1).Her lesion involved the posterio inferior parietal lobule,Brodmann areas (BA)39 and 40 h over and touch their left sid poerir pat of the uerior a for hemipl gia can also be thought of as a disorder of personal awareness. In this condition.patients are aware Clinical Examination of Neglect of their contralesional limb,but are not aware of its paralysis (Bisiach,1993).Anosognosia for Bedside tests for neglect are designed to asses hemiplegia is not an all-or-none phenomenon,and atients' awareness of the contralesional parts of patients may have partial awareness of their con- their own body (personal ntralesiona tralesional weakness (Chatterjee Mennemeier sectors of space eglect)and cor 1996).Misoplegia is a rare disorder in which tralesional s simulta patients are aware of their own limb,but develop an with competing ipsilesional stimuli(extinction) intense dislike for it (Critchley.1974). Personal Neglect Extrapersonal Neglect Personal neglect refers to neglect of contralesiona Extrapersonal neglect can be assessed using bedside parts wn tasks such as line bisection.cancellation,drawing dy. ents groor ally pro and reading.Line bisection tasks assess a patient's ability to estimate the center of a simple stimulus Patients wh perso left sideo their body migh Patients are asked to place a mark at the midpoint of lines (usually horizontal).The task is generally e a c or m eup,or might not shave the left side of their face(Beschin Robertson, 99 administered without restricting head or eye move- To assess personal neglect,patients are asked about ments and without time limitations.Patients with their left arm after this limb is brought into their left-sided neglect typically place their mark to the
easily and remained at home much of the time. Her magnetic resonance imaging (MRI) scan showed an ischemic stroke in the posterior division of the right middle cerebral artery (figure 1.1). Her lesion involved the posterior inferior parietal lobule, Brodmann areas (BA) 39 and 40 and the posterior part of the superior temporal gyrus, BA 22. Clinical Examination of Neglect Bedside tests for neglect are designed to assess patients’ awareness of the contralesional parts of their own body (personal neglect), contralesional sectors of space (extrapersonal neglect), and contralesional stimuli when presented simultaneously with competing ipsilesional stimuli (extinction). Personal Neglect Personal neglect refers to neglect of contralesional parts of one’s own body. Observing whether patients groom themselves contralesionally provides a rough indication of personal neglect. Patients who ignore the left side of their body might not use a comb or makeup, or might not shave the left side of their face (Beschin & Robertson, 1997). To assess personal neglect, patients are asked about their left arm after this limb is brought into their view. Patients with left personal neglect do not acknowledge ownership of the limb. When asked to touch their left arm with their right hand, these patients fail to reach over and touch their left side (Bisiach, Perani, Vallar, & Berti, 1986). A phenomenon called anosognosia for hemiplegia can also be thought of as a disorder of personal awareness. In this condition, patients are aware of their contralesional limb, but are not aware of its paralysis (Bisiach, 1993). Anosognosia for hemiplegia is not an all-or-none phenomenon, and patients may have partial awareness of their contralesional weakness (Chatterjee & Mennemeier, 1996). Misoplegia is a rare disorder in which patients are aware of their own limb, but develop an intense dislike for it (Critchley, 1974). Extrapersonal Neglect Extrapersonal neglect can be assessed using bedside tasks such as line bisection, cancellation, drawing, and reading. Line bisection tasks assess a patient’s ability to estimate the center of a simple stimulus. Patients are asked to place a mark at the midpoint of lines (usually horizontal). The task is generally administered without restricting head or eye movements and without time limitations. Patients with left-sided neglect typically place their mark to the Anjan Chatterjee 2 Figure 1.1 Contrast-enhanced magnetic resonance image showing lesion in the posterior division of the right middle cerebral artery, involving the inferior parietal lobule and the posterior superior temporal gyrus